1. Field of the Invention
The present invention relates to a control system/method for limiting the torque applied to vehicular drivelines. In particular, the present invention relates to controls for vehicular powertrains including an electronically controlled engine and a drivetrain having a limited torque transfer capacity wherein the value of a control parameter indicative of operating conditions at which potentially undesirably high torque loads in the drivetrain may occur (for example, engaged gear ratio and/or vehicle speed) are monitored and engine output (flywheel) torque is limited during the occurrence of potentially undesirably high driveline torque loading operating conditions. More particularly, the present invention relates to controls for controlling engine flywheel torque to protect the vehicle drivetrain while allowing other engine torque parameters, such as accessory torque, to assume necessary values.
2. Description of the Prior Art
Vehicular powertrains for vehicles including fuel-controlled engines, such as diesel engines, and drivetrains including a multiple-speed, change-gear transmission and a drive axle, are well known in the prior art. Examples of such vehicular powertrains and components thereof may be seen by reference to U.S. Pat. Nos. 3,105,395; 3,448,635; 4,361,060; 4,977,972; 4,595,986; 5,033,795 and 5,305,213, the disclosures of which are incorporated herein by reference.
Electronically controlled engines which include an engine microprocessor control and which communicate with other vehicle systems or controllers, such as the transmission controller, over electronic data links are also known in the prior art. Typically, the engine controller and data link operate in accordance with an industry standard protocol, such as SAE J-1922, SAE J-1939, ISO 11898 or the like.
Prior art powertrain systems were not totally satisfactory, as, if sized to handle the maximum torque loading at low-speed operation, they were oversized for the majority of operating conditions and, if sized to handle the normally expected torque loads, were subject to damage at low-speed operation where the engine may generate a maximum or "burst" torque output.
Control systems which controlled an engine torque value, often a gross engine torque value, to protect the vehicle driveline are known in the prior art, as may be seen in U.S. Pat. No. 5,679,096 and aforementioned allowed, copending U.S. Ser. No. 08/560,458, the disclosures of which are incorporated herein by reference.
These prior art engine torque control systems were not satisfactory, as a control parameter other than flywheel torque (such as gross engine torque) was controlled, which might needlessly limit the ability of the engine to generate torque to drive accessories and/or torque to overcome engine friction.